This invention relates to apparatus for deploying safety signs and/or crossing arms as used, for example, on school buses. Of interest in this area are U.S. Pat. Nos. 4,816,804, 4,916,372 and 5,036,307. Throughout the patent application various patents have been cited. The text of each and every cited patent is herein incorporated by reference.
As shown for example in the above patents or as shown in other Patents, for example, U.S. Pat. No. 4,559,518, apparatus for operating school bus safety devices, e.g., signs and arms, are well known. These apparatus include circuits and actuators for deploying a safety device such as a stop sign outwardly from the side of a stopped school bus to alert nearby motorists to stop when the bus is stopped to pick up or discharge passengers. The sign is deployed when the school bus stops and opens its door to permit passengers to alight or depart. A switch coupled to the door opens or closes in accordance with the door open and closed condition. For example, the switch typically closes when the door opens to activate the deployment apparatus.
When the door closes, the switch opens and the apparatus is caused to retract the sign, arm or other device. These apparatus may also be provided to operate a crossing arm on the front bumper to insure that the passengers on departure walk well in front of the bus. Also stop lights attached to the bus may be used in conjunction with the operation of the sign deployment mechanism as shown for example in U.S. Pat. No. 4,559,518. The lights provide further stop signals to approaching motorists.
Often, such apparatus is used in cold climates where the winter is harsh. The apparatus should be sufficiently rugged and reliable to operate in a wide assortment of climatic conditions, including high moisture, temperatures below freezing and so on. The prior art does not specifically deal with these extreme conditions and therefore such apparatus may be subject to potential failure at a critical time.
These safety devices provide an attractive target to be pushed away from such deployed position or pulled outwardly from such retracted position. In the prior art, patent 4,559,518 discloses a two way hinge spring which can be physically moved or stopped in motion. When the physical stop is removed the mechanism will deploy the apparatus to its intended position with full spring force. In U.S. Pat. Nos. 4,916,372 and 5,036,307 a breakaway link system to pivot the apparatus is disclosed. In the event of a mechanical force being applied, the drive mechanism will travel to its intended open or closed position. When the mechanical force is removed the arm will deploy or retract under full spring tension. This can be damaging to a person or to the apparatus. In U.S. Pat. No. 4,983,949 a friction clutch drive system is shown. In the event of an external mechanical force being applied, the drive mechanism continues to drive the mechanism and the clutch slips. This action can prematurely wear the components of the system.